1. Field of the Invention
The present invention relates to an automatic system for assembling and welding different models of car bodies, and is suitable for high mass production.
The system of the invention is not only suitable for manufacturing such bodies, but is also suitable for manufacturing other types of metal sheet articles different from car bodies.
2. Description of Related Art
Systems for manufacturing car bodies are already known, and they provide a single station including power forming machines and welding machines, this station being a point of confluence for the various components arriving by means of conveying systems, generally of the overhead type.
Such systems have, however, restricted application, since they are capable of obtaining only one basic type of product with few changes.
Flexibility (i.e. the possibility to work on a number of basic types during the same activity period) is in fact obtainable by said first approach only if there is a number of fixed stations comprised of power forming machines and welding machines gang-arranged, involving high costs and large dimensions.
Also systems with carousel line on-floor are known, which systems include in lieu of a single station, an assembly carousel continuously moving and comprised of a plurality of carriages spaced apart along the carousel, each carriage including fixtures for supporting the chassis or the bottom of the car body to which are automatically coupled lateral forming machines for the body sides carried by a "parallel" overhead conveying system which is synchronized with the carousel.
This second type of system is a flexible one, since it permits work on different types of car bodies because the lateral forming machines can be of different types and stored at the head of the line without interference with the production process. This system exhibits, however, some limitations because its welding equipment is generally manual since it is susceptible only with difficulties to be automated by means of robots and since the number of the necessary forming machines is very high.
Also, automatic working systems with multiple welding machines provided with welding yokes on board of the forming machines have been proposed, but such systems do not use robots. With such a system, the welding operations are already automated but production flexibility is completely missing in a single production unit. As in the first approach, in order to obtain flexibility a plurality of ganged units is necessary, with the ensuing disadvantages as mentioned above. On the other hand, if only a single unit is present, long periods of time are necessary to replace any specific fixture.
In the Italian patent application No. 67563 A/77, there is disclosed a single fixed working station in which lateral forming machines movable in longitudinal direction are operating, in order to work on different types of car bodies. Welding systems are provided, according to this type of device, on board of said station. As pointed out above, this latter device is different from the other above cited approaches in that it permits, in addition to the flexibility characteristic, tack-welding in a fixed position and automatically by means of robots.
However, even this latter device has some drawbacks which are of not insiginificant from a practical point of view, because it presupposes, on the one hand, the availability of some area for accumulation of the forming machines, which area is not always available in the plant, and, on the other hand, it compels formation of stations for waiting only and thus not necessary for the production process.
Other systems for assembly and welding operations on car bodies are disclosed for example in our Italian patent applications No. 23102 A/82, 22376 A/83, 22377 A/83 and 22575 B/83, in the name of the same Applicant.